Fatality Calculations for Falling UAS

These warnings and alerts are difficult for me to write because I want to provide information to allow UAS pilots to make informed decisions and not to be an alarmist.

The UK AAIB just released a new detailed report on a December 2019 crash of a DJI Matrice 600. In that report, they mention the work of the Dropped Object Prevention Scheme (DROPS).

They state, “The AAIB is not aware of any research relating to the potential for injury from a falling UAS. However, in the 1990’s a dropped object prevention scheme (DROPS) was introduced as part of a safety initiative by the UK Oil and Gas industry. The program has since expanded to include about 200 organisations, with the development of a DROPS analysis calculator. This provides an indication as to the possible outcome of a blunt object in free fall striking a person wearing personal protective equipment (ie hard hat, eye protection).

Analysis using the DROPS calculator indicated that a blunt object with a mass of more than 2 kg (the mass of the accident aircraft was 12.8 kg) falling from a height of 6 m (~20 ft) agl (the approximate height that the aircraft fell from the roof of the house) could result in a fatal injury to someone wearing a hard hat.”

After the crash of a DJI Matrice 210 by a past student of mine I used the DROPS calculator to see what the results would be for the DJI Matrice 210 configuration I flew and other public safety pilots do fly.

The aircraft data is:
DJI Matrice 210: 13.5 lb
TB55 Batteries (2): 3.9 lb
FLIR XT: 0.6 lb
Zenmuse Z30: 1.2 lb
TOTAL: 19.2 lb

Using the DROPS calculator that is embraced as an authoritative resource, if the DJI Matrice 210 in the above configuration fell from six feet or more above ground level and struck someone wearing a hard hat the calculator shows the injury could be fatal.

You can access the DROPS calculator online here.

As a comparison, a DJI Mavic would have to fall from a height of more than 46 feet above ground to result in the same fatal result.

According to the calculations, all UAS can cause a fatal injury if it falls out of the sky and strikes a person. It just depends on weight and height. And keep in mind this industry-accepted calculator is assuming the person struck is wearing a hard hat.

My advice is to avoid flying over any people, at all costs.


John Wakie from FDNY sent me an exceptional paper by Andrew Shelley on this subject that was published in 2016.

The paper is “A Model of Human Harm from a Falling Unmanned Aircraft: Implications for UAS Regulation” and was included in the International Journal of Aviation, Aeronautics, and Aerospace.

This paper includes calculations to determine fatalities for peoplenot wearing hard hats.

The paper cites a number of fatal accidents that would be similar to a UAS flight failure.

“Below is a short list of UAS and model aircraft-related fatalities:

  • In April 2003, an out-of-control model aircraft killed a 14-year old girl in England (Sapsted, 2003).
  • In November 2003, a 41-year-old man was killed while providing flight instruction to the operator of a radio-controlled model helicopter (“Man killed by model helicopter,” 2003).
  • In March 2013, a radio-controlled helicopter crashed in Borneo, Malaysia, killing an 18-month-old baby (“Baby killed,” 2013).
  • In July 2013, a man was killed in Japan while operating a Yamaha R-max UAS (“Heli pilot killed in Japan,” 2013).
  • In September 2013, a 19 year old in New York was killed when his remote controlled helicopter “plummeted from the sky,” inflicting severe head and neck injuries (Zennie, 2013).
  • In Switzerland in 2013, a radio-controlled helicopter struck the 41-year-old man who was operating it, inflicting what was described as “severe head and arm injuries” (Curtis, 2013).”

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